The present invention relates to a resistance micro-bolometer thermal infrared detector. Unlike a conventional resistance bolometer that is an electronically passive device, the present invention is for a detector that can be operated in various electronically active modes, hence the term active bolometer.
The concept of a thin film resistance bolometer has been known for many years, and a description can be found in various publications. See, for example, U.S. Pat. Nos. 4,574,263, 5,369,280, and 5,300,915, for a description of micro-bolometer operation and recent technologies.
Conventional resistance bolometers are essentially passive devices, in that they function as a simple resistor component in an electronic circuit. In operation as an infrared detector the electrical resistance is caused to change by an incremental amount following radiation exposure as a consequence of the temperature coefficient of resistance of the detector material, and this resistance change is detected as a change in electrical current flowing through the detector. The operation and performance of the detector is determined by the external applied bias, signal conditioning, and signal processing circuits.
In the case of a focal plane array of such detectors, small changes in material and dimensional parameters results in ‘fixed pattern’ noise, which must be corrected before the array can be usefully employed. The functionality and detective performance is limited by parameters such as resistivity and temperature coefficient of resistance, which are properties of the specific heat sensitive material employed in the detector.
It is an object of the present invention to provide for a bolometer that overcomes at least some of these problems or provides the public with a useful alternative.